Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
June 25, 2019, 12:46:32 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 2 3 4 5 6 [7] 8 9   Go Down
Print
Author Topic: Horsa-ing around  (Read 6339 times)
0 Members and 1 Guest are viewing this topic.
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #150 on: May 20, 2019, 02:21:54 PM »

abl > ...CTP...current on non-powered ...
His last check flight at the Co. Aerodrome was on the Walthew MK II and he didn't do the aeroplane, ground staff or himself any harm so we assume he's competent.

abl > ...usual newsreel agencies...
Invitations have been extended to Gaumont-British, Pathe Gazette and Movietone. As yet no replies have been received.   However the Co. does confidently expect both the local Scout troop and members of the Saltmarsh-On-Thames (Artistic) Photographic Society to turn up with an assortment of image recording apparatus.

Or...
If the wind drops in the next half hour or so, and as I write it's showing no signs of doing so, I'll* plod along to the aerodrome with my trusty Box Brownie and see what kind of beast we have.


Lurk

*MrsLurker when asked if she would care to accompany me to a flying event (Ox. FF. Portmeadow, last year) unhestitatingly and with not a little emphasis replied, "I'd rather chew off my own foot."  It has become a catch-phrase hereabouts.  Ah me.  You just can't get the ground crew these days, can you? Smiley
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #151 on: May 20, 2019, 04:38:36 PM »

> ...so we assume he's competent.
Turns out he isn't.

Mixed results.  Test glides are satisfactory, but cannot get a good launch off the bungee.

Representative test glide here.  https://vimeo.com/337370215

Left turn is expected, trim tab set left.

Launches, even low power ones are characterised by a steep climb sometimes turning into a loop followed by a short stally flight. 
This one  https://vimeo.com/337371020 is reasonably representative. That flight is with about 1/16" packing under the wing TE and enough lead in the ballast chamber to give a good test glide.

The first bungee launch was so bad, head first CFIT, that TL472 has a sprung canopy, some torn tissue and two cracked longerons on bay 1 on the port side. Despite this it survived another half hour or so of less than soft landings.  Thank goodness for a side keel eh?

You might be surprised to hear that I'm moderately pleased with this evening's results.  The test glides show that it will fly if I can sort out the launch and, unlike the Swallow's first serious outing where I came back with a 17/8 wing, I've come back with a more or less intact model.

Currently scratching my head as to what the issue is.  If anyone has any good ideas I'd be pleased to hear them.

Initial design review. Might be better off with 18swg piano wire for the main leg of the nose wheel.
Attached files Thumbnail(s):
Re: Horsa-ing around
Re: Horsa-ing around
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,905



Ignore
« Reply #152 on: May 20, 2019, 08:16:49 PM »

The glide looks quite reasonable and stable however it's dynamic stability may be a bit low with the long nose leading to inertia problems perhaps. Other than taming the climb on tow by  moving the hook a bit further forward and thus reducing the chance of releasing into a stall I'm not sure what I would do.

If I'm correct about the dynamic effects on the stability than adding extra weight to the nose to stop the stall may make the situation worse when it does stall.

The tow hook position could be a little deceptive due to the depth of the fuselage - what may appear to be too far forward could in effect be the correct position. I would suggest check the position relative to the cg by holding the model upside down from the hook  and see if it hangs around 15deg tail down.

John

Logged
JEM
Bronze Member
***

Kudos: 1
Offline Offline

Australia Australia

Posts: 45




Ignore
« Reply #153 on: May 20, 2019, 09:45:45 PM »

I'm no expert on FF and can't offer any worthwhile advice but I have been following this post since day 1 and find it very entertaining and interesting. Keep it up guys. Well done. Cheesy
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #154 on: May 21, 2019, 12:30:03 AM »

Quote from: OZPAF
> ...Other than taming the climb on tow by  moving the hook a bit further forward
> ... what may appear to be too far forward ..

OK. The hook is roughly 60 deg ahead of the experimentally determined CG, because of the skid, which I thought was pushing it a bit.  In fact I was considering mounting a hook on the skid at about the 30deg point, but in light of your comments will abandon that idea.  A very quick check (fuselage only) shows it is hanging from the hook almost exactly 15 deg. tail down, will try again after work with the wing in place.

Quote from: OZPAF
...dynamic stability may be a bit low ..
Hmm.  Not sure what I can do about that.  This version has more longitudinal dihedral than the original which was 0-0. Plan is now +2 and a bit on the wing and a similar amount negative on the stab.  Perhaps increase the chord on the stab by tacking some sheet to the TE or would that make it worse?

Quote from: OZPAF
If I'm correct about the dynamic effects on the stability than adding extra weight to the nose to stop the stall ...
That would tally with the sort of behaviour I was seeing last night.  Adding nose weight didn't reduce stall at all.

Quote from: JEM
I'm no expert on FF
And as should be blindingly obvious by now nor am I!

Quote from: JEM
...find it very entertaining..
Thank you, you've been a wonderful audience. I'm here all week and don't forget to tip the waitress.  Cheesy
Logged
Jack Plane
Platinum Member
******

Kudos: 34
Offline Offline

United Kingdom United Kingdom

Posts: 1,414




Ignore
« Reply #155 on: May 21, 2019, 03:18:33 AM »


... and don't forget to tip the waitress.  Cheesy


I clocked her quite early on in fact...  Wink

A most excellent entertainment indeed dear Lurk.

Re the launch, might I venture to suggest that - in the interests of scale fidelity - you acquire a DC3 or similar and conduct a proper aero-tow?
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #156 on: May 21, 2019, 03:32:43 AM »

Quote from: Jack Plane
Re the launch, might I venture to suggest that - in the interests of scale fidelity - you acquire a DC3 or similar and conduct a proper aero-tow?

I am seriously considering mounting the hook just in front of the nosewheel.  This would be near scale for an AS 58, TL472 was a 58, which was towed from the nosewheel leg. Smiley
Logged
abl
Gold Member
*****

Kudos: 16
Offline Offline

United Kingdom United Kingdom

Posts: 317


Andy Blackburn



Ignore
« Reply #157 on: May 21, 2019, 03:47:42 AM »

Thinking back a considerable number of years to when I did this sort of thing, I seem to remember that if it's climbing too steeply and/or looping off the tow then the tow-hook is too far back. If you have the hook far enough forward, it won't climb very much at all and will just accelerate in a more-or-less a straight line.

My suggestion would be to try the nosewheel hook, but be prepared to install another one slightly further forward than half-way between that and the current position.
Logged
cvasecuk
Silver Member
****

Kudos: 4
Offline Offline

United Kingdom United Kingdom

Posts: 211



Ignore
« Reply #158 on: May 21, 2019, 05:59:18 AM »

The hand glide looks spot on but the bungee launch looks more like a catapult launch! Either try thinner elastic for a gentler climb or, as others say, move the hook forward.
Ron
Logged
dputt7
Platinum Member
******

Kudos: 90
Offline Offline

Australia Australia

Posts: 1,954




Ignore
« Reply #159 on: May 21, 2019, 06:02:43 AM »

   I'll just add my agreement to those that suggest the hook is too far back, in my experience the hook position is very critical and even dependant on conditions on the day.   While playing with Bungee launches I found an adjustable hook almost necessary, just a bent wire loop wide enough to accept a couple of self tappers that screw into a block glued into the fuselage. I'd start the rearmost position just in front of the position it is now and make the adjustment at least an 1'' long. Just read  Rons post and agree also.
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #160 on: May 21, 2019, 06:41:17 AM »

Quote from: Omnes (and as if with one voice)
...move the hook forward..
I was hoping that this would, as Abl noted, sacrifice climb and height for stable and safe launching which I'll take.  It also reduces the risk of the tow snagging on the nosewheels which I think happened on one of the even less successful launches.
 
Quote from: cvasecuk
... thinner elastic...
It had crossed my mind and I do need to try that for the VMC Osprey, but if I can I'd really like to get this one flying off a "standard" 1/8" bungee, but if needs must then that will be tried.

Quote from: dputt7
... adjustable hook ...
Idea noted.  If we can get it flying with the hook right forward then an update to the plan to provide for a relocatable hook will be made.

Thanks for the suggestions.  It's appreciated.
Lurk.
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,905



Ignore
« Reply #161 on: May 21, 2019, 08:56:44 PM »

Quote
Perhaps increase the chord on the stab by tacking some sheet to the TE or would that make it worse?

Extra damping from increased tail area would help with a minimum increase in tail weight. It may only need a slight increase in chord - 5%? to improve the situation.

John

Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #162 on: May 22, 2019, 01:41:09 AM »

Thanks for that John. Five per cent is just under 4mm so if it does need a deeper stabilizer that's easily accommodated on this build and it's a trivial change to the plan. 

It's patched up, just waiting the second coat of dope on the replacement panel and a new tow-hook in the noseblock. So will try that before modifying the stab.  Hoping for a calm this evening because it looks as though the breeze will be picking up over the next 3 to 5 days.

A question for the house.  I have notes, courtesy of Abl, for an RC assisted variation of this beastie which leads me to wonder; is it reasonable to assume that there would be no need to deepen the stab for an RC version as the model would be flying controlled rather than free? 

Lurk.
Logged
abl
Gold Member
*****

Kudos: 16
Offline Offline

United Kingdom United Kingdom

Posts: 317


Andy Blackburn



Ignore
« Reply #163 on: May 22, 2019, 04:28:31 AM »

Quote from: Omnes (and as if with one voice)
...move the hook forward..
I was hoping that this would, as Abl noted, sacrifice climb and height for stable and safe launching which I'll take.  It also reduces the risk of the tow snagging on the nosewheels which I think happened on one of the even less successful launches.
 ...

Well, it may not sacrifice climb and height because it's too far the other way at the moment; one would hope that optimising the tow-hook position might also optimise the climb and height.

On the tailplane area for R/C, experience suggests that models can be made to fly R/C with less tailplane area, but this is really guided free-flight so personally, I'd go with whatever size is required for F/F. And I think John is probably right about the effect of adding a bit of sheet to the TE, it probably wouldn't do any harm to try a bit more, say a 1/4" wide strip?
« Last Edit: May 22, 2019, 04:40:26 AM by abl » Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,905



Ignore
« Reply #164 on: May 22, 2019, 05:19:29 AM »

Quote
is it reasonable to assume that there would be no need to deepen the stab for an RC version as the model would be flying controlled rather than free? 
It is. How much could be tolerated of course depends on the pilot.

The effect on the FF model should provide a better idea.

John
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Free Flight Vagrant



Ignore
« Reply #165 on: May 22, 2019, 05:26:15 AM »

From looking at the video there are a couple of things you might try.

One - the bungee looks a bit fierce and too short. What is the spec? The model is very small and light and needs a really soft long pull rather than a short sharp one. The Peterborough 36" glider bungee is 7.5m of 1/8" rubber but this will launch pretty heavy models. A combination of too strong a pull and lots of decalage means an early loop off the line.

Two - you might want to try launching with more of a nose up attitude. The model will kite up with the line pulling at around 70 degrees from horizontal - in other words try launching it with 60-70 degrees nose up and a little vertical push into the air at flying speed. The flat launch you are doing at the moment causes the model to accelerate to a high airspeed and pitch up. This is probably responsible for the model popping off the line as it over rotates. Have a look at my Skiddoo launch: https://www.youtube.com/watch?v=S8GhpdDMMZ4 This shows what I mean about launching straight into kiting speed and attitude.

Three - the hook angle may be a little too obtuse. You might want to 'tighten' it a little. But go carefully to avoid hang ups.


I would try one and two before you move the hook position. (You may actually have it too far forward at the moment but you won't know if the previous are also off.)

Jon
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #166 on: May 22, 2019, 10:40:13 AM »

Yak 52> ...bungee looks a bit fierce and too short. What is the spec?
A twiddle under 7m of 1/8" strip, but the fishing line section is shorter than std Peterborough cos my test flying is on a small field.  Might be the foreshortening effect of the camera.

Yak 52 > ...The model is very small and light
But, but, but ... it's 7 or so times heavier than my Lacey M-10 and has 3 times the span.  It's an absolute porker! Smiley  Well it is by my standards.  FWIW my 35" span Swallow which clocks in at about 85g vs the 80g(ish) of the Horsa launches happily from this rig as does the Walthew MKII which is about 65g.

Yak 52 > ... a really soft long pull rather ...
Yeah, that was sort of what I was trying to do and failing miserably.  There was very little tension on the rubber at all, p'raps three or four paces worth which, based on my experience with the Walthew MKII, should have taken it up to no more than 20'  feet or so.

Yak 52 > ...you might want to try launching with more of a nose up attitude.
Yak 52 > ... in other words try launching it with 60-70 degrees nose up and a little vertical push into the air at flying speed
Yak 52 > ...hook angle may be a little too obtuse. You might want to 'tighten' it a little. But go carefully to avoid hang ups.

Thanks for that lot Jon.    It's left me scratching my bald old bonce wondering quite what to for the best, but it's more things to try which can only be good.  Can't it? Smiley

Logged
DavidJP
Titanium Member
*******

Kudos: 43
Offline Offline

United Kingdom United Kingdom

Posts: 2,734




Ignore
« Reply #167 on: May 22, 2019, 11:10:24 AM »

Coincidentally Lurk I came on here just now to say almost exactly what John has said because I was consulting the ravings of a long standing chum who knows a fair bit about such things.  Immediately the fierceness of the pull was offered, followed by the other gifts from Jon. So in short you have two great minds thinking alike.  I hope it all goes well!!   You certainly have the commitment.
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #168 on: May 22, 2019, 01:03:36 PM »

I see; at least one of you thinks I should be committed for my own safety.  Fair enough, fair enough.  Or did I misread that? Smiley

Okaaay.  The current plan is.

  • Try and get a stable launch to low height accepting possible dynamic instability.
  • Modify stab. should it be necessary.

Which breaks down as

  • Finish repairs this evening. I.e. stick the canopy back on.
  • Try and work out a way of tacking on a 4mm strip to the stab without introducing any unwanted elevator effect with a view to fitting at later point.
  • Try Yak 52's and DavidJP's Consulting Guru's advice regarding alterations to take-off using the current hook position.

If that doesn't work...

  • If possible repair any damage. With optional crying into beer.
  • Ponder further on tow hook position.




Logged
Indoorflyer
Gold Member
*****

Kudos: 12
Offline Offline

United States United States

Posts: 503




Ignore
« Reply #169 on: May 22, 2019, 02:38:43 PM »

Kinda hard to see the tow details, but this is an encouraging video:

https://www.youtube.com/watch?v=s8qIfv3tWCU
Logged

Make the same mistake on both sides; nobody will notice...
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #170 on: May 22, 2019, 02:57:38 PM »

That's a stunningly good looking model, much much closer to scale than mine, and it flies very well too.  Now why couldn't I find that plan when I went looking for one? Smiley

As for the tow position; if you pause the video at 10s to 11s, as the model turns to the right at the top of the launch, the pennant which is very close to the fuselage looks to be somewhere about the position of the skid.  Nowhere near the nosewheel.  Sort of suggests that the current tow hook position on mine may be in about the right place. Mebbe.

It also looked like a pretty flat launch to me.

Just about to wander along to the aerodrome.  Fingers crossed I don't stuff it up too badly this time.
Logged
TheLurker
Gold Member
*****

Kudos: 21
Offline Offline

United Kingdom United Kingdom

Posts: 595


Topic starter


Ignore
« Reply #171 on: May 22, 2019, 04:16:48 PM »

Well, looks like I have delivered the disaster promised in the opening post.  So no ticket monies will be refunded. Smiley

Check gliding.  Lovely.  

Bungee launch.  Ah, no.  First attempt; low tension on line, so about four, five paces, angled launch, climbs gently loses all foward velocity nose goes over straight in from 10 or 12 feet.  Crack!  Check it over OK one sprung longeron, we'll try a variation.  Bit more tension p'raps. Not a good idea.  See the pics. Extra bonus before pic!

If anyone is keeping score it's currently Gravity 1, Lurker Industries nil after a late kick-off.


  • If possible repair any damage. With optional crying into beer.

Damn and blast!  No beer because it's a school night.

Almost all the longerons in bay No. 1 gone for a burton, bulkhead No. 1 in bits, cockpit section of keel gone.  The good news is that the remaining parts of the top,bottom and side keels are intact so I think I may be able to repair it, but it won't be quick.  The bigger bits of bulkhead No. 1 have been tacked together with aliphatic to stop the damage getting worse.  

Plan is to cut new F1 pieces  - just as well I kept the templates eh? - and glue them behind the existing F1. Reinstate cockpit keel to get nose re-aligned then let new longerons in, offset from the existing line, into F1,F2.  If it works then I will be fitting a tow hook right forward and trying that.  Effort?  Probably no more than 5 or 6 hours, so about a week, week and half elapsed.  

Paging Mr. Fardell, paging Mr. Fardell. Will Mr. Fardell please take his welding torch to Lurker Industries. Smiley
Attached files Thumbnail(s):
Re: Horsa-ing around
Re: Horsa-ing around
Re: Horsa-ing around
Re: Horsa-ing around
Logged
TimWescott
Gold Member
*****

Kudos: 14
Offline Offline

United States United States

Posts: 941



Ignore
« Reply #172 on: May 22, 2019, 06:43:21 PM »

If it's any consolation, reading "D-Day" by Stephen Ambrose I get the impression that disassembly on landing is a scale maneuver for a combat glider.
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,905



Ignore
« Reply #173 on: May 22, 2019, 07:34:26 PM »

Lousy luck Lurk. I noticed in the video of the other Horsa that the tail is considerably larger than scale! It's rectangular - wider and longer also I feel. This may be the only solution.

John
Logged
abl
Gold Member
*****

Kudos: 16
Offline Offline

United Kingdom United Kingdom

Posts: 317


Andy Blackburn



Ignore
« Reply #174 on: May 23, 2019, 03:09:26 AM »

Bad luck, Lurk.

If it's any consolation, the repairs probably won't take as long as you think.
Logged
Pages: 1 2 3 4 5 6 [7] 8 9   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!